A female mosquito can be difficult to avoid since she tracks our CO2 exhalations, body heat, and body odor. Unfortunately, some of us are “mosquito magnets” who receive more our fair share of bites. There are several popular beliefs as to why someone is a favored snack by these pesky mosquitos. This includes your blood type, your blood sugar level, by eating garlic or bananas, by being a woman, or by being a child. However, according to Leslie Vosshall, director of Rockefeller University’s Laboratory of Neurogenetics and Behavior, there is little trustworthy data to support most of these views.
This is why Vosshall and a former postdoc in her lab, Maria Elena De Obaldia, set out to test the leading explanation to explain varied mosquito appeal: individual odor differences linked to skin microbiota. They recently proved in a research that fatty acids emitted from the skin may produce a powerful aroma that mosquitoes cannot resist. On October 18, they published their findings in the journal Cell.
According to Vosshall, there’s a very, very significant link between having a lot of these fatty acids on your skin and being a mosquito magnet.
Nobody wants to win this competition
Eight participants in the three-year trial were instructed to wear nylon stockings over their forearms for six hours a day. This procedure was performed several times over the course of several days. The investigators employed a two-choice olfactometer assay that De Obaldia designed, consisting of a plexiglass chamber separated into two tubes, to which both ends in a box that housed a stocking, to test the nylons against each other in all conceivable pairings over the following few years.
In the main room, they introduced Aedes Aegypti mosquitos—the leading vector species for Zika, dengue, yellow fever, and chikungunya—and watched as the insects flew down the tubes towards one nylon or the other.
Subject 33 was by far the most tempting target for Aedes aegypti, being four times more enticing to the mosquitos than the next most attractive research participant and an incredible 100 times more appealing than the least attractive, Subject 19.
Because the samples in the experiments were de-identified, the experimenters had no idea which subject wore which nylon. Nonetheless, scientists would realize something peculiar was going on in every study including Subject 33 because insects would flock to that sample.
The subjects were divided into high and low attractors, and the investigators set out to find out what made them distinct. They employed chemical analysis techniques to discover 50 molecular components that were found in high-attracting individuals’ sebum (a moisturizing barrier on the skin). They noticed that mosquito magnets produced much more carboxylic acids than the less attractive participants. These chemicals are found in sebum and are utilised by microorganisms on our skin to create our own human body odor.
Vosshall’s team enrolled additional 56 persons in a validation study to validate their findings. Subject 33 was once again the most appealing, and he remained so throughout time.
De Obaldia somehow concluded that if a person was a mosquito magnet, they remained a mosquito magnet.
Even knockoff finds us
Humans primarily emit two types of scents, which mosquitos detect using two distinct kinds of odor receptors: Orco and IR receptors. To investigate if they could produce mosquitos that couldn’t detect people, the researchers generated mutants that were missing one or both of the receptors.
Orco mutants preserved their attraction to humans and were able to discriminate between mosquito magnets and low attractors, whereas IR mutants lost their attraction to humans to varied degrees but retained the capacity to find us.
These findings support one of Vosshall’s previous investigations, which highlighted the redundancy of Aedes aegypti’s extraordinarily sophisticated olfactory system. The female mosquito depends on it to survive and reproduce. She can’t do either without blood. That’s why, according to Vosshall, “she has a backup plan and a backup plan and a backup plan and is sensitive to these variances in the skin chemistry of the people she goes after.”
The seeming indestructibility of the mosquito smell tracker makes it impossible to imagine a world in which humans are not the main course. However, one possible approach is to modify our skin microbiomes. Slathering the skin of a high-appeal individual, such as Subject 33, with sebum and skin germs from a low-appeal person, such as Subject 19, might produce a mosquito-masking effect.
“That experiment hasn’t been conducted”, says Vosshall. “That’s a difficult experiment. But, if that were to succeed, you might envision that by using a nutritional or microbiome intervention in which bacteria on the skin are able to modify how they interact with sebum, you could transform someone like Subject 33 into Subject 19. But all of it is theoretical.”
“I think it would be very, really amazing to figure out whether this is a universal impact,” says Vosshall, adding that she and her colleagues hope this article will motivate researchers to explore other mosquito species, including those in the genus Anopheles, which carries malaria.